This invention generally relates to a tracking-error correcting apparatus for use in an apparatus of the type wherein signal information is recorded in parallel skewed tracks on a record medium and has particular application to a video tape recorder (VTR) in which stop-motion, slow-motion or fast-motion pictures as well as normal-motion pictures can be reproduced.
In a conventional VTR, a rotary transducer head assembly is provided with one or more magnetic transducers which scan successive parallel tracks on a magnetic record tape so as to record and/or reproduce video signals in such tracks. In general, while the one or more transducers rotate across the tape, the tape itself longitudinal direction thereof. A typical VTR includes one, and preferably two, record and/or playback transducers mounted on a suitable rotary assembly so as to rotatably scan a magnetic tape which is helically wrapped about at least a portion of a guide drum forming a part of the transducer assembly. During recording, a tracking servo system controls the rotation of the transducers with respect to the tape movement, and control pulse signals are recorded on a marginal portion of the tape. During reproduction, the same or a similar servo control system is used to synchronize the movement of the tape to the rotation of the transducers in accordance with the recorded control pulse signals. Consequently, an accurate video picture can be displayed in response to the reproduced video signal. This accuracy is, in large part, due to the fact that the servo control system tends to control the relative movement and position between the rotary transducers and the tape such that each transducer scans substantially the same track during reproduction operation as was scanned during the recording operation. Therefore, during normal tape speed (normal mode), the servo system serves to insure that the scanning path of the heads substantially coincides with the previously recorded tracks.
Recently, many VTR systems have been provided with various reproducing operations, such as "stop or still-motion", "slow-motion" and "quick or fast-motion". In these various reproducing modes, the tape speed differs from the speed during the recording mode. Consequently, the scanning path is different from the recorded track during these different reproducing modes, that is the scanning path is inclined, or angularly disposed, with respect to the recorded track. Thus, in various modes other than "normal operation", guard band noise and cross-talk with result due to tracking errors or scanning deviation. Generally, upon leaving the prerecorded track, the transducer starts scanning a guard band disposed in-between recorded tracks. Accordingly, the output signal of the transducer will be reduced and contain a noise component. On the other hand, as the transducer starts scanning the next recorded track, the transducer picks up signals from two adjacent tracks resulting in cross-talk. This tracking error due to the variation in the tape speed results in a deterioration of the reproduced pictures.